Collision du Ka 4 avec un obstacle lors de l'atterrissage à l'aéroport de Montricher

Le 3 juillet 1972, un vol d'entraînement impliquant un Alexander Schleicher Ka 4 Rhönlerche II a eu lieu près de l'aéroport de Montricher, en Suisse. Le pilote élève, sous la supervision d'un instructeur, a tenté d'atterrir sur la mauvaise piste en raison d'une désorientation. L'instructeur est intervenu mais trop tard, ce qui a entraîné la collision du planeur avec une haie. Les deux occupants sont restés indemnes, et le planeur a subi des dommages mineurs. L'accident a été attribué à l'intervention tardive de l'instructeur lors d'une approche finale à basse altitude.

1. Aerotow training flight: A dual training flight in the Rhönlerche II HB-592 departed Montricher by aerotow with a student flying under instructor supervision.
2. Wrong runway selected: After release and two right-hand turns, the student initiated an approach to runway 03, mistakenly ignoring that runway 21 remained in use with a moderate to strong southwesterly wind.
3. Delayed instructor action: The instructor allowed the student to persist in planning the incorrect runway approach and only briefly took control once the error was evident, redirecting late toward the runway 21 circuit.
4. Low altitude on circuit: By abeam the runway threshold on downwind for runway 21, the glider’s height had reduced to about 120 m AGL and continued to decrease rapidly during a shortened base leg.
5. Late dive to clear hedge: On final, after crossing the BAM Apples–L’Isle railway line, the instructor took control and pushed the glider into a dive attempting to clear a 4–5 m high hedge about 175 m before the runway 21 threshold.
6. Impact with hedge: The glider failed to clear the obstacle, the left wing struck a branch, and the aircraft was further slowed by bushes at the hedge line.
7. Crash - no injury: The glider came to rest at the edge of the hedge near the runway with minor damage and both occupants uninjured.